1. Technical Field
The present invention relates in general to an improved process for manufacturing carbon nanotubes and, in particular, to an improved system, method, and apparatus for continuous synthesis of single-walled carbon nanotubes.
2. Description of the Related Art
Currently, production of single-walled carbon nanotubes (swcnt) is substantially limited to an experimental or laboratory scale with the largest production rates being on the order of only grams per day. There are several different processes that are used for swcnt production, such as laser ablation methods, arc discharge methods, and chemical vapor deposition (CVD) methods. Some of these prior art processes have also combined plasma generation, thermal annealing, and the use of various transition metal catalyst supports with one of the three techniques. See, e.g., U.S. Pat. No. 6,451,175 to Lal; U.S. Pat. No. 6,422,450 to Zhou; U.S. Pat. No. 6,232,706 to Dai; and U.S. Pat. No. 6,221,330 to Moy.
There are a number of problems with these existing, prior art methods. Many of them are batch-type processes that are capable of producing product only once per cycle, rather than producing a continuous supply of end product which would be far more desirable. As a result, the rates of production are relatively low, with some methods generating only enough product to scarcely conduct laboratory testing on the end product. Consequently, it would be very difficult if not impossible to scale these methods up to industrial quantity production levels. The scalability of production methods is critical for many potential industrial applications for swcnt. A few examples include high performance structures manufacturers, such as those in military, aerospace, motorsports, marine, etc., fabrication businesses and, more generally, materials suppliers. The inability to make large quantities of swcnt affordable inherently limits their applications to uses as reinforcements for composites and the like. Unfortunately, swcnt-reinforced composites have a number of limitations themselves, including: fiber/matrix adhesion problems, strength limitations due to matrix design, and only providing incremental improvements in other areas of performance. Furthermore, some prior art methods of producing swcnt make a resultant product that is the relatively low in purity. Thus, an improved process for continuous production of a relatively pure form of swcnt would be highly desirable for many practical applications.